1 //===----------------------------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 // <string> 10 // UNSUPPORTED: c++03, c++11, c++14 11 12 // template<class InputIterator, 13 // class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>> 14 // basic_string(InputIterator, InputIterator, Allocator = Allocator()) 15 // -> basic_string<typename iterator_traits<InputIterator>::value_type, 16 // char_traits<typename iterator_traits<InputIterator>::value_type>, 17 // Allocator>; // constexpr since C++20 18 // 19 // The deduction guide shall not participate in overload resolution if InputIterator 20 // is a type that does not qualify as an input iterator, or if Allocator is a type 21 // that does not qualify as an allocator. 22 23 #include <cassert> 24 #include <cstddef> 25 #include <iterator> 26 #include <string> 27 #include <type_traits> 28 29 #include "test_macros.h" 30 #include "test_allocator.h" 31 #include "min_allocator.h" 32 33 class NotAnIterator {}; 34 using NotAnInputIterator = std::back_insert_iterator<std::basic_string<char16_t>>; 35 36 template <typename T> 37 struct NotAnAllocator { typedef T value_type; }; 38 39 template <class Iter, class Alloc, class = void> 40 struct CanDeduce : std::false_type { }; 41 42 template <class Iter, class Alloc> 43 struct CanDeduce<Iter, Alloc, decltype((void) 44 std::basic_string{std::declval<Iter>(), std::declval<Iter>(), std::declval<Alloc>()} 45 )> : std::true_type { }; 46 47 static_assert( CanDeduce<char*, std::allocator<char>>::value); 48 static_assert(!CanDeduce<NotAnIterator, std::allocator<char>>::value); 49 static_assert(!CanDeduce<NotAnInputIterator, std::allocator<char16_t>>::value); 50 static_assert(!CanDeduce<char*, NotAnAllocator<char>>::value); 51 #ifndef TEST_HAS_NO_WIDE_CHARACTERS 52 static_assert( CanDeduce<wchar_t*, std::allocator<wchar_t>>::value); 53 static_assert(!CanDeduce<wchar_t const*, NotAnAllocator<wchar_t>>::value); 54 #endif 55 56 TEST_CONSTEXPR_CXX20 bool test() { 57 { 58 const char* s = "12345678901234"; 59 std::basic_string s1(s, s+10); // Can't use {} here 60 using S = decltype(s1); // what type did we get? 61 static_assert(std::is_same_v<S::value_type, char>, ""); 62 static_assert(std::is_same_v<S::traits_type, std::char_traits<char>>, ""); 63 static_assert(std::is_same_v<S::allocator_type, std::allocator<char>>, ""); 64 assert(s1.size() == 10); 65 assert(s1.compare(0, s1.size(), s, s1.size()) == 0); 66 } 67 { 68 const char* s = "12345678901234"; 69 std::basic_string s1{s, s+10, std::allocator<char>{}}; 70 using S = decltype(s1); // what type did we get? 71 static_assert(std::is_same_v<S::value_type, char>, ""); 72 static_assert(std::is_same_v<S::traits_type, std::char_traits<char>>, ""); 73 static_assert(std::is_same_v<S::allocator_type, std::allocator<char>>, ""); 74 assert(s1.size() == 10); 75 assert(s1.compare(0, s1.size(), s, s1.size()) == 0); 76 } 77 #ifndef TEST_HAS_NO_WIDE_CHARACTERS 78 { 79 const wchar_t* s = L"12345678901234"; 80 std::basic_string s1{s, s+10, test_allocator<wchar_t>{}}; 81 using S = decltype(s1); // what type did we get? 82 static_assert(std::is_same_v<S::value_type, wchar_t>, ""); 83 static_assert(std::is_same_v<S::traits_type, std::char_traits<wchar_t>>, ""); 84 static_assert(std::is_same_v<S::allocator_type, test_allocator<wchar_t>>, ""); 85 assert(s1.size() == 10); 86 assert(s1.compare(0, s1.size(), s, s1.size()) == 0); 87 } 88 #endif 89 { 90 const char16_t* s = u"12345678901234"; 91 std::basic_string s1{s, s+10, min_allocator<char16_t>{}}; 92 using S = decltype(s1); // what type did we get? 93 static_assert(std::is_same_v<S::value_type, char16_t>, ""); 94 static_assert(std::is_same_v<S::traits_type, std::char_traits<char16_t>>, ""); 95 static_assert(std::is_same_v<S::allocator_type, min_allocator<char16_t>>, ""); 96 assert(s1.size() == 10); 97 assert(s1.compare(0, s1.size(), s, s1.size()) == 0); 98 } 99 { 100 const char32_t* s = U"12345678901234"; 101 std::basic_string s1{s, s+10, explicit_allocator<char32_t>{}}; 102 using S = decltype(s1); // what type did we get? 103 static_assert(std::is_same_v<S::value_type, char32_t>, ""); 104 static_assert(std::is_same_v<S::traits_type, std::char_traits<char32_t>>, ""); 105 static_assert(std::is_same_v<S::allocator_type, explicit_allocator<char32_t>>, ""); 106 assert(s1.size() == 10); 107 assert(s1.compare(0, s1.size(), s, s1.size()) == 0); 108 } 109 110 return true; 111 } 112 113 int main(int, char**) 114 { 115 test(); 116 #if TEST_STD_VER > 17 117 static_assert(test()); 118 #endif 119 120 return 0; 121 } 122